Yes, you can:
sp_configure 'max server memory', <put the max number of MB here>
go
reconfigure with override

Signature
Tom
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Thomas A. Moreau, BSc, PhD, MCSE, MCDBA, MCITP, MCTS
SQL Server MVP
Toronto, ON Canada
https://mvp.support.microsoft.com/profile/Tom.Moreau
Hi,
Can I limit the amount of memory SQL 2005 uses?
I have 4GB in my server and sqlservr.exe uses between 3gb and 3.5gb?
Thanks